Method of separating lignosulfonic acids



METHOD OF SEPARATING LIGNOSULFONIC ACIDS Leif Jantzen, Oslo, Norway, assignor to Arthur C. Trask Company, a corporation of Illinois N6 Drawing. Application April 1, 1955 Serial No. 498,773

s claims. (Cl.260-124) and about 10% inorganic material. I

The lignosulfonic acids are two general types commonly called high molecular weight or alphalignosulfonic acids and low molecular weight or beta lignosulfonicacids.

.The beta acids contain most of the sulfonic acid groups and'generally make up about one-third of the total amount of lignosulfonic acids present.

The high and the low molecular weight lignosulfonic acids ordinarily have different uses and different chemical characteristics. It has therefore long been known that a separation of the alpha and beta acids is desirable from a commercial standpoint. However, *no satisfactory method of economically separating these acids, particularly on a commercial basis, has heretofore been proposed.

One of the features of this invention is to provide an improved method of separating alpha-high molecular weight lignosulfonic acids and beta-low molecular weight lignosulfonic acids from an aqueous liquid containing a mixture thereof which comprises contacting said liquid with chrome tanned hide for a time sufficient to combine chemically said alpha acids with the tanned hide, washing said tanned hide with an alkali to remove the alpha acids therefrom and activate the tanned hide for reaction with the beta acids, again contacting said liquid from which the alpha acids have thusly been substantially removed with'the tanned hide for a time sufficient to combine chemically said beta acids with the tanned hide, and removing the beta acids therefrom by treating with an alkali.

Another feature of the invention is to provide an improved method of separating alpha-high molecular weight lignosulfonic acids from an aqueous liquid containing said acids comprising treating said liquid with tanned hide containing basic amirio groups for a time suflicient to combine chemically said acid with the tanned hide, andremoving said acids therefrom by treating with an aqueous alkali. v

A further feature of the invention is to provide an improved method of separating lignosulfonic acids from waste sul'fite liquor containing sugars, comprising contacting said liquor with tanned hide containing basic groups for a time sufiicient to combine chemically said acids with the tanned hide, separating the substantially acid free liquor from the tanned hide containing the chemically combined acids and regenerating said acids by treating the hide with an alkali.

A more specific feature of the invention is to provide a method of separating alpha-high molecular weight lignosulfonic acids and beta-low molecular lignosulfouic acids United States Patent Y taining a mixture of these acids.

from each other and from an aqueous liquid containing a mixture of these acids which comprises contacting the liquid with tanned hide for a time sufficient to combine chemically the alpha acids with the tanned hide, washing the hide with an alkali to remove the alpha acids therefrom, again contacting the liquid with the tanned hide for a time sufficient to combine chemically the beta acids with the tanned hide and removing the beta acids therefrom.

Other features and advantages of the invention will be apparent from the following detailed description of the invention.

In the process of this invention, the liquid which is preferably the sulfite liquor from the pulp digester, is contacted with finely divided mineral tanned .hide, and particularly with chrome tanned hide, for a time sufficient for the high molecular weight alpha acids'to combine chemically. with the tanned hide. The chemically combined alpha acids are then removed by washing the tanned hide with an aqueous alkali solution. This separates the acids from the tanned hide in the form of salts and produces hydroxyl groups in the tanned hide.

The treated liquid from which the alpha acids have been thus removed is then again contacted with the thusly treated tanned hide such as by circulating liquid over the tanned hide. This contact is maintained for a time suiticient ,to react substantially all of the beta-low molecular weight acids with the tanned hide. These low molecular weight acids are then removed from the tanned hide by washing with an aqueous alkali solution. Again the beta acids are removed in a form of the salt.

The tanned hide is then returned to a condition chemically for reuse in separating alpha and beta acids by washing with an aqueous acid solution. The thusly treated tanned hide may then again be used in the manner ,described for separating the acids from each other and from a fresh supply of liquid.

As can be seen, the process of this invention is economical and is rapid in its operation. Furthermore, the process lends itself readily to continuous selective separation of the alpha-acids and the beta-acids from a liquid con- In the case of sulfite liquor from the paper pulp process, the alpha acids may be first removed in this manner and then the beta acids may be removed. The sugars may then be separatedfrom the inorganic matter by fermentation of the sugars with any of the many well known fermenting agents in the customary manner.

' The minerally tanned hide, and particularly chrome tanned hide, is used in this process. The raw hide substance is not usable in the process set out herein, because in reacting with the acids in an aqueous solution the raw hide also takes up water and this water causes the hide to swell which hinders the penetration and reaction of the ligno-acids. Furthermore, the raw hide putrifies quite easily. However, when the hides have been tanned with mineral agents and particularly in the well-known chrome process, the chrome combines with the acid groups while the amino groups of the protein are made available for reaction with the lignosulfonic acids. Thus the basic groups of the tanned hide are free to react so that about 2 parts by weight ofchrome'tanned hide will take up. or react with 1 part by weight of high molecular weight or alpha lignosulfonic acids.

The reaction of the high molecular weight lignosulfonic acids with the tanned hide appears to be based upon an ion exchange. Thus, the alpha acids replace any'other acid with a lower molecular weight which may be connected to the basic groups of the tanned hide.

When the liquid containing the mixed. alpha and beta lignosulfonic acids is contacted with chrome tanned hide by filtering the liquid through the tanned hide substantially all of the high molecular weight or alpha acids will be taken up or reacted. If the amount of tanned hide and alpha acids are at the above ratio of about 2 to l by weight, substantially none of the low molecular weight or beta acids will react with the tanned hide. When all of the high molecular weight acids have been bound up in the tanned hide, the filtrate contains only the beta or low molecular weight lignosulfonic acids to gether with the other sulfite liquor materials such as the sugars and inorganic matter. When this filtrate is' then again filtered through tanned hide, the beta acids are absorbed so that only the sugars and the inorganic matter remain in the filtrate.

The principal differences between the high and the low molecular weight acids are shown in the following table:

i lt-rt't'nt. Aver-nun l I -\Vviahl Alpha-Arid Rntli'ttnfinlt i t. 12. ."17 11,1300 Beta-Acid Sodium Salt. I 0.6 5.22 5,1Ht)

moved from the liquor, the tanned hide is washed with an aqueous alkali solution such as a solution of am- I monium hydroxide. The alkali removes the alpha acids from the tanned hide in the form of ammonium lignosulionate. and is replaced by the hydroxyl groups from the alkali connected to the ammonium groups of the tanned hide. In this condition the tanned hide is basic and will take up substantially any acid. However, the liquid from which the alpha acids have been removed in the above described manner is then recirculated through the thusly treated finely divided tanned hide so that the beta acids which now have the highest equivalent weight in the liquid react to become chemically bound to the ammonium groups in the collagen or protein molecule. Thusthe beta acids are removed from the liquid. The beta acids are then separated from the tanned hide by again treating the tanned hide with an alkali such as ammonium hydroxide.

The tanned hide is then reactivated for reuse in a subsequent separation process by treating it with a dilute acid. preferably an aqueous solution of sulfuric acid.

ln a typical example of practicing this invention, 1000 pounds of finely divided chrome tanned hide shavings were treated by recirculating 1000 pounds of waste sulfite liquor containing mixed alpha and beta lignosulfonic acids through the tanned hide. The liquor containedSOO pounds of alpha acids and about 250 pounds of beta acids. The circulation was continued until substantially all of the alpha acids had been reacted and bound up by the tanned hide. The liquor was then removed and the tanned hide was rinsed with a concentrated solution of ammonium hydroxide equivalent to the calculated amount of alpha acids present in the tanned hide.

After the alkali solution now containing the ammonium salt of alpha lignosulfonic acid had been removed from the tanned hide. the tanned hide was again contacted by the liquor which was recirculated over the tanned hide until substantially all of the beta acids had been taken out. The tanned hide was again washed with the ammonium hydroxide solution until substantially all of the beta acids had been separated from the tanned hide. The tanned hide was then treated with a dilute aqueous solution of sulfuric acid to return the tanned hide to its initial condition. The methods of this invention permit many variations in procedure. Thus, the high molecular weight lignosulfonic acids of any sulfite liquor or equivalent liquid may be precipitated by water soluble proteins and the precipitate may then be dissolved with alkalies. The solution may then be treated with chrome tanned hide in the manner set out herein so that the high molecular-weight acids are taken tip by the tanned hide leaving the protein available for reuse. This procedure is important particularly in those instances where the remaining low molecular weight lignosulionic acids are used in chemical processes such as that employed for making vanillin.

In those instances where sulfite liquor is used for precipitation of glu'tanic acid the reaction product of this acid with alpha lignosulfonic acid may be split into its component parts by treating with chrome tanned hide so that the alpha lignosulfonic acids may be recovered and used again.

in another variation the alpha acids can be precipitated from a mixture of alpha and beta acids by using any product capable of precipitating the alpha acids. The low molecular part of the filtrate or beta acids can then be separated from the filtrate and concentrated by the use of chrome tanned hide in the process described above.

In still another variation the alpha acids may be preripitated with water soluble proteins and this product, ligno-glutin, may be used as such. The beta acids may then be separated by the use of chrome tanned hide in the manner described.

While I have shown and described certain embodiments of my invention, it is to be understood that it is capable of many modifications. Changes, therefore, in the invention may be made without departing from the spirit and scope of the invention as disclosed in the appended claims.

I claim:

1. The method of separating alpha-high. molecular weight lignosulfonic acids and beta-low molecular weight lignosulfonic acids from an aqueous liquid containing a mixture thereof which comprises contacting said liquid with chrome tanned hide for a time suflicient to combine chemically said alpha acids with the tanned hide, washing said tanned hide with an alkali to remove the alpha acids therefrom and activate the tanned hide for reaction with the beta acids, again contacting said liquid from which the alpha acids have thusly been substantially removed with the tanned hide for a time sufiicient to combine chemically said beta acids with the tanned hide, and removing the beta acids therefrom by treating with an alkali.

2. The method of treating sulfite liquor from a sulfite paper pulp process to separate selectively alpha-high molecular weight lignosulfonic acids and beta-low molecular weight lignosulfonic acids therefrom which comprises contacting said liquor with chrome tanned hide in an amount of about 2 parts by weight of the tanned hide per part of alpha acids for a time sufficient to combine chemically said alpha acids with the tanned hide, washing said tanned hide with an alkali to remove the alpha acids therefrom as salts and activate the tanned hide for subsequent reaction with the beta acids, again contacting said liquor from which the alpha acids have thusly been substantially removed with the tanned hide for a time sufficient to combine chemically said beta acids with the tanned hide, and washing said tanned hide with an alkali to remove the beta acids therefrom as salts.

3. The method of separating alpha-high molecular weight lignosnlfonic acids from an aqueous liquid containing said acids comprising treating said liquid with chrome tanned hide for a time sufficient to combine chemically said acid with the tanned hide, and removing said acids therefrom by treating with an aqueous alkali.

'4. The method of separating alpha-high molecular weight lignosulfonic acids and beta-low molecular weight lignosulfonic acids from an aqueous liquid containing a mixture thereof which comprises contacting said liquid with tanned hide containing basic groups for a time sufficient to combine chemically said alpha acid with the tanned hide, washing said tanned hide with an alkali to remove the alpha acid therefrom, again contacting said liquid with the tanned hide for a time sufficient to combine chemically said beta acids with the tanned hide, and removing the beta acid therefrom by treating with an alkali.

5. The method of separating alpha-high molecular weight lignosulfonic acids from an aqueous liquid containing said acids comprising treating said liquid with tanned hide containing basic amino groups for a time sufficient tocombine chemically said acid with the tanned hide, and removing said acids therefrom by'treating with an aqueous alkali.

6. The method of treating sulfite liquor from a sulfite paper pulp process to separate selectively alpha-high molecular weight lignosulfonic acid and beta-low molecular weight lignosulfonic acids therefrom which comprises contacting said liquor with tanned hide containing basic.

' thusly been substantially removed with the tanned hide treating said tanned hide with an aqueous acid solution:

to prepare the tanned hide for a subsequent selective separation of alpha and beta acids. 7

7. The method of separating'lignosulfonic acids from .waste sulfite liquor containing sugars, comprising: contacting said liquor with tanned hide containing basic groups for a time sufiicient to combine chemically said acids with the tanned hide; separating the substantially acid free liquor from the tanned hide containing the chemically combined acids; and regenerating said'acids by treating the hide with an alkali.

8. The method of separating lignosulfonic acids from waste sulfite liquor containing sugars, comprising: contacting said liquor with chrome tanned hide for a time s'uflicient to combine chemically said acids with the chrome tanned hide; separating the substantially acid free liquor from the tanned hide containing the chemically combined acids; and washing said tanned hide with an ammonium hydroxide solution to remove said acids therefrom.

References Cited in the file of this patent UNITED STATES PATENTS Van Blaricom et al. June -7, 1955 OTHER REFERENCES 

2. THE METHOD OF TREATING SULFIDE LIQUOR FROM A SULFITE PAPER PULP PROCESS TO SEPARATE SELECTIVELY ALPHA-HIGH MOLECULAR WEIGHT LIGNOSULFONIC ACIDS AND BETA-LOW MOLECULAR WEIGHT LIGNOSULFONIC ACIDS THEREFROM WHICH COMPRISES CONTACTING SAID LIQUOR WITH CHROME TANNED HIDE IN AN AMOUNT OF ABOUT 2 PARTS BY WEIGHT OF THE TANNED HIDE PER PART OF ALPHA ACIDS FOR A TIME SUFFICIENT TO COMBINE CHEMICALLY SAID ALPHA ACIDS WITH THE TANNED HIDE, WASHING SAID TANNED HIDE WITH AN ALKALI TO REMOVE THE ALPHA ACIDS THEREFROM AS SALTS AND ACTIVATE THE TANNED HIDE FOR SUBSEQUENT REACTION WITH THE BETA ACIDS, AGAIN CONTACTING SAID LIQUOR FROM WHICH THE ALPHA ACIDS HAVE THUSLY BEEN SUBSTANTIALLY REMOVED WITH THE TANNED HIDE FOR A TIME SUFFICIENT TO COMBINE CHEMICALLY SAID BETA ACIDS WITH THE TANNED HIDE, AND WASHING SAID TANNED HIDE WITH AN ALKALI TO REMOVE THE BETA ACIDS THEREFROM AS SALTS. 